1. Field of the Invention
The field of the invention is that of adapters or holders for a tool which may be in the form of a bit or tap, the improvements residing in the structure for holding the tool.
2. Description of the Prior Art
Adapters or holders for tools, such as a bit or a tap, have been known in the prior art. In certain known types of these devices, particularly devices which have a quick change capability, the tool has been held by way of spherical balls that have a radial movement and are held against the sides of the tool to hold it in position. Quick change devices of this type typically embody a collar which is movable axially with respect to the body of the adapter or holder for purposes of moving the holding elements radially into holding position and out of holding position into a release position. In devices of the type described, an axially movable collar is provided which when moved axially can engage the holding devices, that is, the spherical balls, to move them inwardly against a holding surface on the tool. The balls move in openings in the side walls of the holder. Reference is made to U.S. Pat. No. 4,234,277.
Holders for tools such as described in the foregoing are subject to a serious deficiency. Since the tool itself is cylindrical, when the balls are moved radially to hold it, they have only a point contact in the case where the balls are held against the cylindrical surface of the tool or otherwise, they only have a limited contact with the tool where the tool is provided with an annular groove.
The herein invention as described in detail hereinafter is one which makes available a construction which fully overcomes the deficiencies of the prior art, particularly the deficiencies referred to in the foregoing.